Major Causes of Water Pollution in Oceans and Coastal Areas

Most of the sources of water pollution that occurs in oceans and coastal areas originates from the land and threatens fish and wildlife, and disrupts marine ecosystems. The coastal parts or areas of the world—especially mangrove swamps, wetlands, coral reefs, and estuaries—usually face most of the negative impacts of the enormous quantities of pollutants and wastes being discharged into surrounding oceans, oftentimes without regulation or control.

With approximately 40% of the world’s population living on or near coastlines, it has been projected that 80% of the marine pollution that originates from land and coastal populations will double by year 2050. According to a research conducted by UNEP (United Nations Environment Programme), between 80% and 90% of the municipal sewage that originates from the coastal areas of less-developed countries is dumped into oceans without undergoing treatment. This is why it’s generally difficult for coastal waters to degrade wastes that originate from coastal areas.

According to a study, an average of one-quarter of the people that use coastal beaches in the USA develop eye irritations, ear infections, respiratory disease, sore throats, or gastrointestinal disease after swimming in oceanwater or seawater that contains bacteria and  infectious viruses. A high percentage of the trash that harbors the bacteria and infectious viruses that originate from land, are washed or poured out of storm drains, and float down to streams and rivers that empty into the ocean and sea. Most of the remaining trash is dumped into the ocean from cruise ships and cargo.

The major causes of water pollution in coastal areas and oceans are as follows:

1. Cruise ships

Many cruise ships cause water pollution in oceans and coastal areas, as they indiscriminately dump wastes without being detected and regulated or controlled. In the waters surrounding the USA, for instance, although dumping of wastes into water bodies is illegal, some cruise ships continue dumping wastes secretively, usually at night. A cruise liner carrying as many as 2,400 cruise members and 6,300 passengers can generate as much waste (garbage, toxic chemicals, waste oil, and sewage) as a small city.

2. Runoff of trash, agricultural wastes, sewage, toxic metals, oil, and sediments from cities

The water in oceans and coastal areas is also being polluted by agricultural wastes and sewage that discharge into them with large quantities of nitrate and phosphate plant nutrients which can cause explosive growths of harmful algae and create dead zones during summer months. Harmful algae can release waterborne and airborne toxins that kill fish, poison seafood, and discourage tourism.

The toxic metals and oil that originate from streets and parking lots usually pollute ocean and coastal area waters. The sewage from cities or environments in coastal areas generate sewage that adds nitrogen and phosphorus to oceans, thereby contributing to water pollution. Bacteria and viruses that originate from sewers and septic tanks contaminate shellfish beds and close beaches, while the runoff of fertilizer from lawns adds nitrogen and phosphorus to oceans and coastal areas.

Sediments and solid wastes from construction sites are usually washed into waterways and end up in oceans, choking ocean plants and fish, clouding waters, and blocking off sunlight. In addition, the runoff of pesticides and manure adds toxins and excess nitrogen and phosphorus to ocean and coastal area waters.

3. Industries

The nitrogen oxides that originate from autos and smokestacks of industries, the toxic chemicals that originate from discarded plastic grocery bag, water bottle, or chips bag produced in industries, and the heavy metals that are produced in industries and discharged in effluents flow into bays and estuaries and find their way to pollute the water in oceans and coastal areas.

4. Oil and oil-rig spill

Studies have shown that the urban and industrial runoff of oil (crude oil and refined petroleum) from land activities constitute the largest source of oil pollution in oceans and coastal areas. Crude petroleum (which is brought out from the ground) and refined petroleum (such as fuel oil, diesel, gasoline, and other processed petroleum products) are often blown out or spilled at offshore oil drilling rigs.

A lot of waste oil originates from leaks in refineries, pipelines, and other oil-handling and storage facilities. In fact, between one-third and one-half of all the oil pollution in oceans originates from oil and oil products that are intentionally dumped or accidentally spilled or leaked on land or into sewers by industries and land or home owners.

Negative impacts of water pollution on life forms existing in oceans and coastal areas

The four major causes of water pollution in oceans and coastal areas, which have been briefly discussed in this post, need to be urgently tackled by pollution prevention measures that can halt further degradation of oceans which are a vital part of the earth’s life-support system.

Without implementing effective pollution prevention measures, excess nitrogen would continue causing explosive growth of toxic microscopic algae which can poison fish and marine mammals; increasing quantities of chemicals and toxic metals would continue contaminating shellfish beds, killing spawning fish, and accumulating in the tissues of the oceans bottom feeders; increasing quantities of sedimentation and algae growth would continue using up oxygen, reducing sunlight, killing beneficial sea grasses, and degrading habitat as well; the volatile organic hydrocarbons in oil/ from oil spills would continue coating the feathers of seabirds and the fur of marine mammals, and continue killing many aquatic organisms, especially in regions or areas where the aquatic organisms or animals are in their vulnerable larval forms.

When oil is spilled into oceans, it coats the bodies of aquatic animals, destroys their natural heat insulation and buoyancy, and causes many of them to drown or die due to exposure from loss of body heat. The heavy oil components that find their way to the bottom of the ocean floor can completely envelope bottom-dwelling organisms such as mussels, crabs, clams, and oysters, mussels, and make them unfit for human consumption, thereby disrupting the livelihoods of the coastal area/Gulf Coast people who depend on fisheries from ocean water, and causing large economic losses for their tourism businesses.